The present invention relates to a selective growth method, and to a semiconductor light emitting device and a fabrication method thereof, to each of which the selective growth method is applied.
GaN based compound semiconductors have become a focus of attention as semiconductor materials for semiconductor light emitting devices, and a variety of device designs and trials have been made to improve characteristics of semiconductor light emitting devices using GaN based compound semiconductors.
The GaN based semiconductor light emitting device emits light having a wavelength in a short-wavelength region, and therefore, it allows emission of light of blue or green. Accordingly, a full-color image display unit can be fabricated, for example, by combining the GaN based semiconductor light emitting devices with GaAs based semiconductor light emitting devices allowing emission of light of red.
The above-described GaN based semiconductor light emitting device can be fabricated by forming a mask having an opening on a sapphire substrate, forming a nitride layer by selective growth from the opening, and sequentially forming a cladding layer, a guide layer, and an active layer on a tilt growth plane of the nitride layer by selective growth. Such a light emitting device is excellent in luminous efficiency.
With respect to selective growth of the active layer, if the active layer is selectively grown on a crystal having different crystal planes or on a crystal having a three-dimensional shape, the number of dangling bonds of atoms or the like may differ between the different crystal planes or between different positions, and therefore, the crystal growth rate and/or the composition of a mixed crystal may differ between the different crystal planes and between the different positions.
In the case of fabricating a semiconductor light emitting device using a gallium nitride based compound semiconductor, when GaN is selectively grown by an MOCVD process, the GaN layer is formed into a triangular stripe or hexagonal pyramid shape having a facet composed of the S-plane. It is well known that the growth rate on the S-plane is low, whereas the growth rate on the C-plane is high. Accordingly, in the case of laminating an active layer made from InGaN or the like on the GaN crystal having the above shape by crystal growth, the thickness of a top portion of the active layer tends to be thick while the thickness of a tilt portion of the active layer tends to be thin; and the content of an element such as indium (In) also tends to be different between the top portion and the tilt portion of the active layer.
In a semiconductor light emitting device, to ensure excellent light emission characteristics, it is preferred that the thickness of an active layer be uniform over the whole region thereof. If the thickness of the active layer is non uniform, there may occur a problem that characteristics of the device are degraded, and more specifically, a half-value width of an emission wavelength peak is reduced, and the repeatability of fabrication is also reduced.